<!doctype html>
<html lang="zh-cn">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .bg {
            height: 666px;
            width: 100%;
            font-size: 60px;
            text-align: center;
        }
        .dialog {
            z-index: 999;
            position: fixed;
            top: 0;
            right: 0;
            bottom: 0;
            left: 0;
            background: rgba(0, 0, 0, 0.5);
        }
        .dialog .content {
            min-height: 300px;
            width: 600px;
            background: #fff;
            border-radius: 5px;
            border: 1px solid #ebeef5;
            box-shadow: 0 2px 12px 0 rgba(0, 0, 0, 1);
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
        }
    </style>
</head>
<body>
<div class="bg">
    页面内容
</div>
<div class="dialog">
    <div class="content">
        弹出框
    </div>
</div>
</body>
</html>